The present invention relates to optical scanning systems and more particularly to a compact portable optical bar code scanner system which can be mounted in or on a checkout counter in which the checkout operator is in a sitting position with respect to the checkout counter.
In present-day merchandising point-of-sale operations, data pertaining to the purchase of a merchandise item is obtained by reading data encoded indicia such as a bar code printed on the merchandise item. In order to standardize the bar codes used in various point-of-sale readout systems, the grocery industry has adopted a uniform product code (UPC) which is in the form of a bar code. Reading systems which have been constructed to read this bar code include hand-held wands which are moved across a label bearing the bar code and stationary optical scanners normally located within the cabinet structure of a checkout counter and in which the bar code label is read when a purchased merchandise item and its associated label aremmoved across a window in the supporting surface of the counter constituting the scanning area of a counter, which movement is part of the process of loading the item in a bag or baggage cart. There has arisen a need for a stationary optical scanner to be installed in a checkout counter in which the operator is required to be in a sitting position at the checkout counter having a table-height construction. In order to meet this requirement, the depth of the optical scanner is required to be very shallow which limits the length of travel of the scanning light beams generated by the optical scanner and therefore the number of scanning lines in the resulting scanning pattern projected to read the bar code label which in turn controls the scanning efficiency of the pattern and the scanner. In the above cited co-pending patent application, a compact optical scanner was constructed to satisfy the above cited requirements. While the compact scanner read coded labels positioned adjacent the scanner at any angle up to 90.degree. to the reading surface of the scanner, the reading performance of the scan pattern for coded labels flush to the surface of the scanner was not optimum because of the low projection angle towards the ends of the diagonal scan lines in the scan pattern which resulted in excessive elongation of the laser beam diameter when the coded label was relatively flush thereto.